This invention relates to shipping containers and more particularly to shipping containers for rolls of flexible sheet or film material.
The shipment of rolls of plastic sheet and film in corrugated boxboard cartons is a widespread practice. The plastic film is wound around a thin hollow cylindrical core and is supported at its ends by a pair of end plates. The end plates are square with each side slightly longer than the outer diameter of the roll, and incorporate a plug for inserting into the core, so that the entire weight of the roll is carried by the end plates. The carton is usually square, and the length of the carton or box is equal to or greater than the width of the roll. Dunnage is used to fill the ends of the carton when the length of the carton is greater than the width of the roll being shipped. A representative roll and carton of this type are shown in U.S. Pat. No. 3,710,539. For shipping, a plurality of rolls (usually four to nine, depending on the size of a roll), packaged in boxboard cartons as described, are placed on a pallet. The rolls are usually stacked either two or three high, and a divider sheet, which is typically made of plywood or fiberboard, is placed between adjacent layers of cartons. The cartons are stacked so that the end plates are aligned. In this way the entire weight of rolls in each stack is transmitted through the end plates to the pallet. The pallet and divider sheet may have cleats to maintain the cartons in alignment. The entire pallet load is unitized by strapping or shrink wrapping.
Packages of rolls in boxboard cartons as above have several disadvantages.
First, boxboard cartons and their contents can be damaged in various ways. There is a danger of crushing a box and damaging its contents due to shifting of a pallet load in transit. The conventional corrugated boxboard carton is not strong enough to withstand the loading imposed by the end plates of a carton stacked thereon. While the cartons are initially stacked so that the end plates of all cartons in a stack are aligned, it is difficult to maintain this precise alignment throughout shipment. The use of a divider sheet lessens but does not entirely eliminate crushing. Cartons can also be damaged by tearing due to the use of metal strapping.
Second, a plant that ships a number of widths of roll goods must either maintain an equal number of lengths of shipping cartons or use dunnage, neither of which is entirely satisfactory. The former requires a large inventory of cartons. The use of dunnage is not desirable because the dunnage may contaminate the plastic film and because the presence of end plates at positions other than the ends of the carton increases the possibility of carton failure under the end plates.
Third, the conventional boxboard packaging entails the use of considerable quantities of non-reusable materials. The boxboard carton and the divider sheet are not reusable, and the pallet is frequently not returned or reused. The use of non-reusable packaging materials in quantity present a waste disposal problem and is ecologically undesirable.